1. Technical Field
The present invention relates to an MRI (magnetic resonance image) joint (articulation) imaging system for imaging a joint portion of a human body (patient) by changing the bending angle thereof with the use of the MRI system.
2. Description of the Related Art
Recently, with the development of medical diagnosis systems, MRI system have been widely used. In the MRI system, a magnetic resonance image can be obtained by applying an RF pulse in a predetermined pulse sequence and an inclination magnetic field to an object to be imaged (placed in a predetermined static magnetic field) and then collecting and processing echo signals generated from the object to be imaged.
As one of the imaging techniques using the MRI system, there exists such a method where a knee joint of a patient is imaged by changing the bending angle thereof gradually so that the obtained image can be displayed as a cinematic image (motion picture). In more detail, as shown in FIG. 1, a plurality of images 1, 2 and 3 of different bending angles of the knee joint are continuously formed to obtain a cinematic image 4.
To obtain the cinematic image 4, a fixing apparatus as shown in FIG. 2 has been used so far. In the fixing apparatus shown in FIG. 2, a fixing base 8 is placed under a knee joint 7 of a patient 6 lying down on a top board 5, and the knee joint 7 is fixed to the top board 5 by use of two belts 9. That is, under the condition that the knee joint 7 is slightly bent, the knee joint 7 is covered with an RF coil 10 to obtain an MR image.
After that, the leg position of the patient 6 is moved upward by use of a leg mounting base 11 to obtain a status in which the knee joint is stretched. Under these conditions, the stretched knee joint is imaged to obtain anther MR image. When the above-mentioned imaging is repeated by changing the bending angle of the knee joint gradually, it is possible to obtain the cinematic image as shown in FIG. 1.
For the cinematic image taken based upon the conventional fixing method, however, since the operator must change the bending angle of the knee joint 7 of the patient 6 in a scanning room for each image, there exists a problem in that the operation is troublesome. In addition, since the bending angle is adjusted manually, a difference in the incremental change in angular position of the knee joint is inevitably produced between the respective images, with the result that the motion of the cinematic image is not uniform.